The invention is particularly well suited for use in a galvanizing process which uses powderized zinc for contacting a strip of metal that has been freshly dipped in a bath of liquid zinc. In such processes, it is important to remove the fine zinc dust or powder from the gas being exhausted from the process into the ambient atmosphere, since the dust contaminates the atmosphere and zinc powder is wasted. Therefore, the powder laden exhaust gas is circulated through filters which remove the zinc powder, prior to discharging the exhaust gas into the ambient atmosphere. Such filters become clogged with zinc powder, if they are not periodically cleaned. The invention is directed to an improved device for cleaning filters shown, for example, in U.S. Pat. No. 4,233,041 which relates to the backflushing of filters with air.
Briefly stated, the invention is in a filtering device for removing finely powderized material from a stream of gas. The device comprises a closed chamber which has a vertically disposed axis about which are equally spaced a plurality of filters which have identical openings that are in a horizontally disposed bottom wall of the chamber. Means are provided for removing filtered gas from the device. Means are supplied for cleaning the filters, including a drive shaft that is coincidental with the vertical axis of the chamber and an arm which is coupled to the drive shaft for unitary rotation about the vertical axis of the chamber, the arm extending in a radial direction from the drive shaft and terminating at a free distal end which is designed to arcuately move a cover from opening-to-opening, the cover being dimensioned to individually cover and seal each opening from the chamber. The cover has a vertically extending member which is freely mounted on the distal end of the arm for movement in at least a vertical direction, so that the cover is slidably supported on the bottom wall of the chamber. Means are included for rotating the drive shaft and arm about the vertical axis of the chamber, whereby the cover is moved from opening-to-opening, so that the filters can be successively cleaned of the finely powderized material.